Photoacoustic gas detection device and method based on gas filtering

Abstract

The invention provides a photoacoustic gas detection device and method based on gas filtering, a motor drives a gas filter wheel to replace a chopper to modulate a light source, and the problem that absorption interference of background gas cannot be well solved by a mainstream spectrum gas detection method can be solved; the photoacoustic spectrum sensing device is used as a detection unit and has the advantage that the zero background and the detection sensitivity are in direct proportion to the excitation light power, and the structure of a mainstream photoacoustic spectrum gas sensing system is simplified while the beneficial effect of restraining background gas absorption interference is achieved; the problems that an infrared detector serves as a detection unit and is easily influenced by temperature and detection signals are saturated in the prior art of gas filtering can be solved. According to the invention, high-selectivity, high-sensitivity and high-precision detection of the target gas under background gas absorption interference is realized, effective detection of one or more target gases can be realized, and the detection cost is further reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of gas detection, and in particular relates to a photoacoustic gas detection device and method based on gas filtering. Background Art

[0002] The spectral methods for gas detection mainly include tunable laser absorption spectroscopy (TDLAS), cavity ring-down absorption spectroscopy (CRDS), differential optical absorption spectroscopy (DOAS) and photoacoustic spectroscopy (PAS). Among them, photoacoustic spectroscopy (PAS) is an indirect absorption spectroscopy detection technology that has developed rapidly in recent years. It measures the acoustic wave signal generated by the incident laser of the target gas through a photoacoustic cell, a tuning fork quartz crystal or a cantilever beam, and uses the relationship that the acoustic wave signal is proportional to the gas concentration to calculate the concentration information of the target gas. In addition, the advantages of photoacoustic spectroscopy such as zero background, no wavelength selectivity, detection sensitivity proportional to the excitation light power, small size, fast response and low cost make it widely used in the field of gas monitoring. However, these spectral methods use the relationship between the absorption of the target gas to a specific wavelength laser and the concentration of the target gas to invert the target gas concentration information, and at this specific wavelength, there is not only the absorption of the target gas, which causes the absorption interference problem of the background gas at this specific wavelength. Therefore, effectively solving the absorption interference of the background gas plays a very critical role in improving the sensitivity of the system.

[0003] In addition, most existing spectral gas detection technologies use near-infrared or mid-infrared light sources. Usually, the spectral intensity of the target gas in the mid-infrared is 3 to 4 orders of magnitude stronger than that in the near-infrared. For example, the absorption line intensity of CO at 1568 nm is 2.221×10 -23 cm / molecule, 4.465×10 at 4.6 μm -19 cm / molecule, which means that the same device will be much more sensitive in the mid-infrared, but the mid-infrared laser is expensive, which greatly increases the system cost and is not conducive to production. The cost of broadband light sources in the mid-infrared is much lower, and it is usually combined with narrow-band filters for spectral gas detection. However, the price of narrow-band filters is generally high, and there may be multiple gas absorptions within the bandwidth of the narrow-band filter, which affects the performance of the system. Summary of the invention

[0004] In order to solve the above problems existing in the prior art, the present invention provides a photoacoustic gas detection device and method based on gas filtering. The technical problem to be solved by the present invention is achieved through the following technical solutions:

[0005] In a second aspect, the present invention provides a photoacoustic gas detection device based on gas filtering, comprising: a light source and a motor driving device, a gas filter wheel device and a photoacoustic spectroscopy gas sensing device;

[0006] The light source and motor drive device are used to generate a light source and send the light source into the gas filter wheel device in a collimated manner;

[0007] The gas filter wheel device is used to rotate at a predetermined frequency so that the light source enters the sealed gas chamber containing the target gas and the sealed gas chamber containing pure nitrogen respectively, and then passes through the sealed gas chamber to enter the photoacoustic spectroscopic gas sensing device; wherein the light source that penetrates into the sealed gas chamber containing the target gas is partially absorbed, and the light source that penetrates into the sealed gas chamber containing pure nitrogen is not absorbed;

[0008] The photoacoustic spectroscopy gas sensing device is used to utilize its own mixed gas to absorb part of the light source that passes through a sealed gas chamber containing a target gas and a sealed gas chamber containing pure nitrogen and enters itself, and correspondingly generates a reference photoacoustic signal and a measurement photoacoustic signal.

[0009] In a second aspect, the present invention provides a photoacoustic gas detection method based on gas filtering, using the photoacoustic gas detection device based on gas filtering described in the first aspect to detect the mixed gas to be detected, and obtain a reference photoacoustic signal and a measurement photoacoustic signal;

[0010] The concentration of the mixed gas to be measured is determined by using the difference between the reference photoacoustic signal and the measured photoacoustic signal.

[0011] Beneficial effects:

[0012] 1. The present invention is based on gas filtering technology and utilizes a gas filter wheel to solve the problem of background gas absorption interference that the mainstream spectral gas detection method cannot solve well;

[0013] 2. The present invention uses a photoacoustic spectroscopy sensing device as a detection unit, which has the advantages of zero background and detection sensitivity proportional to the excitation light power. While bringing the beneficial effect of suppressing background gas absorption interference, it simplifies the structure of the mainstream photoacoustic spectroscopy gas sensing system, and can solve the problem that the existing gas filtering related technology uses an infrared detector as a detection unit, which is easily affected by temperature and has detection signal saturation;

[0014] 3. The present invention uses a motor-driven gas filter wheel to replace the chopper to achieve modulation of the light source, which can further reduce system costs;

[0015] 4. The light source used in the present invention can be a narrowband light source or a broadband light source. The use of a broadband light source can effectively reduce system costs.

[0016] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the appearance structure of a photoacoustic gas detection device based on gas filtering provided by the present invention;

[0018] Figure 2 It is a schematic diagram of the overall structure of the photoacoustic gas detection device based on gas filtering provided by the present invention;

[0019] Figure 3 It is a structural schematic diagram of the appearance of a gas filter wheel device including four sealed air chambers provided by the present invention;

[0020] Figure 4 It is a schematic diagram of the absorption curves of the target gas and the background gas within the laser light source band provided by the present invention. DETAILED DESCRIPTION

[0021] The present invention is further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0022] like Figure 1 As shown, the present invention provides a photoacoustic gas detection device based on gas filtering, comprising: a light source and a motor driving device 5, a gas filter wheel device 6 and a photoacoustic spectroscopy gas sensing device 7;

[0023] The light source and motor drive device 5 is used to generate a light source and send the light source into the gas filter wheel device 6 in a collimated manner;

[0024] refer to Figure 2 The light source and motor driving device 5 of the present invention comprises: a light source 8, a beam collimating device 9, a motor 10, and a rotating shaft 11; the light source 8 is a narrowband light source or a broadband light source. The light source 8 is used to generate a laser with a specific wavelength; the specific wavelength corresponds to the absorption spectrum of the target gas; the beam collimating device 9 is used to collimate the laser and output it; the motor 10 is used to connect the rotating shaft 11 to drive the gas filter wheel device 6 to rotate so that the laser enters it.

[0025] It is worth noting that the beam collimating device 9 is mainly composed of a collimating lens, the purpose of which is to better collimate the light source into the subsequent light path, namely the gas filter wheel device 6 and the photoacoustic spectroscopic gas sensor device 7. The purpose of the motor 10 is to drive the gas filter wheel device 6 to rotate to achieve modulation of the light source.

[0026] The gas filter wheel device 6 is used to rotate at a predetermined frequency so that the light source enters the sealed gas chamber containing the target gas and the sealed gas chamber containing pure nitrogen respectively, and then passes through the sealed gas chamber to enter the photoacoustic spectroscopic gas sensing device 7; wherein the light source penetrating into the sealed gas chamber containing the target gas is partially absorbed, and the light source penetrating into the sealed gas chamber containing pure nitrogen is not absorbed;

[0027] Combination Figure 2 and Figure 3 The gas filter wheel device 6 includes a gas filter wheel 12, and the gas filter wheel 12 includes a high-concentration target gas closed air chamber 13 and a pure nitrogen closed air chamber 14; the gas filter wheel 12 is used to be controlled by the light source and the motor driving device 5 and rotate at a predetermined rotation frequency, thereby driving the high-concentration target gas closed air chamber 13 and the pure nitrogen closed air chamber 14 to rotate, so that the laser enters the high-concentration target gas closed air chamber 13 and the pure nitrogen closed air chamber 14 respectively, and then passes through the two closed air chambers to enter the photoacoustic spectroscopic gas sensor device 7, and the rotation frequency is the same as the resonance frequency of the photoacoustic spectroscopic gas sensor device 7.

[0028] The gas concentration contained in the high-concentration target gas sealed air chamber 13 is set according to the absorption spectrum, and the concentration setting enables the target gas to be absorbed by the laser, and the gas concentration is close to 100%. The number of the high-concentration target gas sealed air chamber 13 is one or more, and the number of the pure nitrogen gas sealed air chamber 14 is one. The target gas contained in each of the high-concentration target gas sealed air chambers 13 is different, and the time period during which the light source enters the high-concentration target gas sealed air chamber 13 containing different target gases is different during the rotation process, and the mixed gas to be measured includes background interference gas and target gas.

[0029] It is worth noting that the gas filter wheel 12 is a rotating wheel comprising two or more sealed air chambers, the number of which is the number of target gases plus one, one of which is filled with pure nitrogen, and the other rotating wheels are respectively filled with corresponding high-concentration target gases.

[0030] The photoacoustic spectroscopy gas sensing device 7 is used to utilize its own mixed gas to absorb part of the light source that passes through the sealed gas chamber containing the target gas and the sealed gas chamber containing pure nitrogen and enters itself, and correspondingly generates a reference photoacoustic signal and a measurement photoacoustic signal.

[0031] refer to Figure 2 The photoacoustic spectroscopy gas sensing device 7 of the present invention comprises: an acoustic spectroscopy gas sensing device 15, wherein the acoustic spectroscopy gas sensing device 15 comprises a detection element, an air inlet 16 and an air outlet 17;

[0032] The mixed gas to be measured enters from the gas inlet 16 and exits from the gas outlet 17; the detection element is used to detect the acoustic wave signal generated by the absorption of the mixed gas to be measured, the acoustic wave signal generated and detected by the laser passing through the high-concentration target gas sealed air chamber 13 is the reference photoacoustic signal, and the acoustic wave signal generated and detected by the laser passing through the pure nitrogen sealed air chamber 14 is the measurement photoacoustic signal. The detection element is one of a photoacoustic cell, a tuning fork quartz crystal oscillator or a cantilever beam.

[0033] The laser intensity modulated by the gas filter wheel 12 enters the photoacoustic spectroscopy gas sensor device 7, and is absorbed by the gas to be measured to generate an acoustic wave signal. The acoustic wave signal generated by the laser passing through the high-concentration target gas sealed gas chamber 13 and detected is the reference photoacoustic signal S ref The acoustic wave signal generated by the laser passing through the pure nitrogen sealed gas chamber 14 and detected is the measured photoacoustic signal S mea By analyzing S mea -S ref , the absorption coefficient α of the target gas in the gas to be measured can be obtained gas , and then the concentration information of the target gas in the gas to be measured is inverted through the formula α=σN.

[0034] The present invention utilizes the reference photoacoustic signal and the measurement photoacoustic signal for analysis, and can obtain the concentration of the target gas contained in the mixed gas to be measured.

[0035] During the rotation process, the laser enters different sealed gas chambers at different time periods, that is, in the same rotation cycle, if there are multiple sealed gas chambers 13 with high concentration target gas, each sealed gas chamber enters the laser at different time periods, and the laser that subsequently enters the photoacoustic spectroscopic gas sensor device 7 also corresponds. For a mixed gas to be measured containing multiple target gases, the concentration of each target gas in the mixed gas to be measured can be obtained in different time periods.

[0036] In a second aspect, the present invention provides a photoacoustic gas detection method based on gas filtering, using the photoacoustic gas detection device based on gas filtering according to the first aspect to detect the mixed gas to be detected, and obtain a reference photoacoustic signal and a measurement photoacoustic signal;

[0037] The concentration of the mixed gas to be measured is determined by using the difference between the reference photoacoustic signal and the measured photoacoustic signal.

[0038] The present invention can utilize a photoacoustic gas detection device based on gas filtering to detect the mixed gas to be detected, obtain a reference photoacoustic signal and a measurement photoacoustic signal, and then upload them to a host computer for analysis.

[0039] The gas concentration detection principle of the present invention is described in detail below.

[0040] The intensity of the laser light source with a specific wavelength corresponding to the absorption line of the gas is a function of the wavelength λ, expressed as I 0 (λ), according to the Beer-Lambert law, the intensity of the transmitted light after interacting with the gas of length L is I out (λ) can be expressed as:

[0041] I out (λ)=I 0 (λ)exp(-α(λ)L) (1);

[0042] Where α(λ) is the absorption coefficient of the target gas.

[0043] The gas filter wheel designed in the present invention comprises two or more sealed gas chambers. However, when the measured photoacoustic signal is used to invert the target gas concentration information, only the photoacoustic signal generated by the laser passing through the two gas chambers filled with pure nitrogen and high-concentration target gas on the gas filter wheel needs to be considered. Therefore, it is assumed that the absorption spectrum of the target gas corresponds to the wavelength band of the laser light source with a specific wavelength as λ. source , then this band can be considered to be composed of the following four bands:

[0044] λ 0 : The wavelength range that neither the target gas (gas) nor the background interference gas (background) absorbs;

[0045] λ gas : The wavelength range where only the target gas absorbs;

[0046] λ background : The wavelength range where only background interfering gas absorbs;

[0047] λ gas / background : The wavelength range absorbed by both the target gas (gas) and the background interference gas (background).

[0048] like Figure 4 As shown, range 1 represents the wavelength range λ of the laser light source source , Range 2 represents the wavelength range λ where only background interfering gas absorbs background , range 3 represents the wavelength range λ absorbed by both the target gas and the background interference gas gas / background , range 4 means that only the target gas absorbs the wavelength range λ gas , the remaining part after removing 2, 3, and 4 from range 1 is the wavelength range that neither the target gas nor the background interference gas absorbs (λ 0 ).

[0049] Since the laser passes through the closed gas chamber filled with high concentration target gas on the gas filter wheel, its light intensity within the absorption wavelength range of the target gas will be completely absorbed, leaving only λ 0 and λ background The laser within this band is not absorbed, so the light intensity of this part of the laser is I ref It can be expressed as:

[0050]

[0051] The laser light passing through the gas chamber filled with pure nitrogen on the gas filter wheel will not be absorbed, so the light intensity I mea It can be expressed as:

[0052]

[0053] It is known that the relationship between the photoacoustic signal intensity S(λ) measured by the photoacoustic spectroscopy gas sensor device and the gas absorption coefficient α(λ) is as follows:

[0054] S(λ)=A·I(λ)·α(λ) (4);

[0055] Where A is the photoacoustic cell constant and I(λ) is the intensity of the laser.

[0056] Since the light intensity of the laser after passing through the gas chamber filled with high concentration target gas on the gas filter wheel within the absorption wavelength range of the target gas has been completely absorbed by the high concentration target gas, the photoacoustic signal obtained by entering the photoacoustic spectroscopy gas sensor device is not affected by the target gas, but only generated by the background interference gas, that is, the background interference gas is in the λ background The photoacoustic signal is generated by absorbing light intensity in the band, so the photoacoustic signal, that is, the reference photoacoustic signal S ref , which can be expressed as:

[0057]

[0058] In the formula, α background (λ) is the background interfering gas absorption coefficient.

[0059] The laser passing through the gas chamber filled with pure nitrogen on the gas filter wheel is not changed before entering the photoacoustic spectroscopic gas sensor device, so the photoacoustic signal obtained by entering the photoacoustic spectroscopic gas sensor device will be generated by the target gas and background interference gas in the mixed gas to be measured, that is, the target gas to be measured and the background interference gas are in λ gas , background , gas / background The photoacoustic signal is generated by absorbing light intensity within the wavelength range, so the photoacoustic signal, that is, the measured photoacoustic signal S mea , which can be expressed as:

[0060]

[0061] In the formula, α gas (λ) is the absorption coefficient of the target gas in the mixed gas to be measured.

[0062] Subtracting equation (5) from equation (6) yields:

[0063]

[0064] Theoretically, the absorption lines of the target gas and the background interference gas in the mixed gas to be measured will not overlap. It is only due to the broadening effect of the absorption line that the overlapping band λ gas / background The absorption of the target gas and background interference gas in the mixed gas to be measured in this band is very small and can be ignored. Therefore, the photoacoustic signal generated in this band can also be ignored, that is, the last two terms of formula (7) can be ignored, so the formula can be simplified as follows:

[0065]

[0066] In addition, it is known that the relationship between the gas absorption coefficient α and the gas concentration N can be expressed as:

[0067] α=σN (9);

[0068] Where N is the concentration of the target gas in the mixed gas to be measured, σ is the absorption cross section of the target gas in the mixed gas to be measured, and α gas is the absorption coefficient of the target gas in the mixed gas to be measured, S mea is the measured photoacoustic signal, S ref is the reference photoacoustic signal, I 0 (λ) is the laser intensity, λ gas Indicates the wavelength range where only the target gas absorbs. α is the general expression of the absorption coefficient of the target gas in the mixed gas to be measured. α=α gas .

[0069] Furthermore, no matter the gas detection device is composed of a gas filter wheel including two or more sealed gas chambers, when analyzing the concentration of a target gas in the mixed gas to be tested, it is only necessary to analyze the photoacoustic signals generated by the laser passing through the two gas chambers filled with pure nitrogen and high concentration target gas on the gas filter wheel, that is, by measuring the reference photoacoustic signal S ref and measure the photoacoustic signal S mea , and analyze S by formula (8) mea -S ref The absorption coefficient α of the target gas in the gas to be measured can be obtained gas, and then substitute it into formula (9) to invert the concentration information of the target gas in the gas to be tested. Therefore, through the gas detection device based on gas filtering designed by the present invention, high-sensitivity and high-precision detection of one or more gases can be achieved under the interference of background gas absorption.

[0070] If the infrared broadband light source can be used without using a filter, the system performance can be improved while ensuring that the system cost is not too high. The present invention uses a driving gas filter wheel to replace the chopper to achieve light source modulation, which can further reduce system costs.

[0071] In order to achieve high-sensitivity and high-precision detection of three target gases (gas1, gas2, gas3) under the interference of background gas absorption, it is necessary to Figure 1 The gas filter wheel device (including two sealed gas chambers) in the gas detection device system shown in FIG. Figure 3 A gas filter wheel assembly comprising four sealed gas chambers is shown.

[0072] like Figure 3 As shown in FIG. 1 , the gas filter wheel device comprises four sealed gas chambers, which are respectively filled with pure nitrogen, high-concentration target gas gas1, high-concentration target gas gas2 and high-concentration target gas gas3. Thus, the acoustic wave signal generated by the laser passing through the pure nitrogen sealed gas chamber and detected is the measured photoacoustic signal S mea The acoustic wave signal generated by the laser passing through the closed gas chamber with high concentration target gas gas1 and detected is the reference photoacoustic signal S ref-gas1 The acoustic wave signal generated by the laser passing through the closed gas chamber with high concentration target gas gas2 is the reference photoacoustic signal S ref-gas2 The acoustic wave signal generated by the laser passing through the closed gas chamber with high concentration target gas gas3 is the reference photoacoustic signal S ref-gas3 .

[0073] By analyzing S mea -S ref-gas1 , S mea -S ref-gas2 and S mea -S ref-gas3 , the absorption coefficients α of the three target gases in the gas to be measured can be obtained respectively gas1 , α gas2 and α gas3 , and then the concentration information of the three target gases in the gas to be tested is inverted through the formula α=σN.

[0074] It is worth noting that the terms "first" and "second" in the present invention are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0075] Although the present application is described herein in conjunction with various embodiments, in the process of implementing the claimed application, those skilled in the art may understand and implement other variations of the disclosed embodiments by reviewing the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude a plurality of components or steps.

[0076] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A photoacoustic gas detection device based on gas filtering, characterized in that: include: A light source and motor driving device (5), a gas filter wheel device (6) and a photoacoustic spectroscopy gas sensor device (7); The light source and motor drive device (5) is used to generate a light source and send the light source into the gas filter wheel device (6) in a collimated manner; The gas filter wheel device (6) is used to rotate at a predetermined frequency so that the light source enters the sealed gas chamber containing the target gas and the sealed gas chamber containing pure nitrogen respectively, and then passes through the sealed gas chamber to enter the photoacoustic spectroscopic gas sensing device (7); wherein the light source that penetrates into the sealed gas chamber containing the target gas is partially absorbed, and the light source that penetrates into the sealed gas chamber containing pure nitrogen is not absorbed; The photoacoustic spectroscopy gas sensing device (7) is used to utilize its own mixed gas to be measured to absorb part of the light source that enters itself through a sealed gas chamber containing the target gas and a sealed gas chamber containing pure nitrogen, and to generate a reference photoacoustic signal and a measurement photoacoustic signal accordingly.

2. The photoacoustic gas detection device based on gas filtering according to claim 1 is characterized in that: The light source and motor driving device (5) comprises: a light source (8), a light beam collimating device (9), a motor (10), and a rotating shaft (11); The light source (8) is used to generate laser light of a specific wavelength; the specific wavelength corresponds to the absorption spectrum of the target gas; The beam collimating device (9) is used to collimate the laser for output; The motor (10) is used to connect to the rotating shaft (11) to drive the gas filter wheel device (6) to rotate so that laser light can enter therein.

3. The photoacoustic gas detection device based on gas filtering according to claim 2 is characterized in that: The light source (8) is a narrowband light source or a broadband light source.

4. The photoacoustic gas detection device based on gas filtering according to claim 1 is characterized in that: The gas filter wheel device (6) comprises a gas filter wheel (12), and the gas filter wheel (12) comprises a high-concentration target gas sealed chamber (13) and a pure nitrogen sealed chamber (14); The gas filter wheel (12) is used to be controlled by the light source and the motor drive device (5) to rotate at a predetermined rotation frequency, thereby driving the high-concentration target gas sealed chamber (13) and the pure nitrogen sealed chamber (14) to rotate, so that the laser light enters the high-concentration target gas sealed chamber (13) and the pure nitrogen sealed chamber (14) respectively, and then passes through the two sealed chambers to enter the photoacoustic spectroscopic gas sensor device (7), and the rotation frequency is the same as the resonance frequency of the photoacoustic spectroscopic gas sensor device (7).

5. The photoacoustic gas detection device based on gas filtering according to claim 4 is characterized in that: The number of the high-concentration target gas sealed air chambers (13) is one or more, and the number of the pure nitrogen gas sealed air chamber (14) is one.

6. The photoacoustic gas detection device based on gas filtering according to claim 5 is characterized in that: Each of the high-concentration target gas sealed air chambers (13) contains different target gases, and during the rotation process, the light source enters the high-concentration target gas sealed air chambers (13) containing different target gases at different time periods, and the mixed gas to be measured contains background interference gas and target gas.

7. The photoacoustic gas detection device based on gas filtering according to claim 1 is characterized in that: The photoacoustic spectroscopy gas sensing device (7) comprises: an acoustic spectroscopy gas sensing device (15), wherein the acoustic spectroscopy gas sensing device (15) comprises a detection element, an air inlet (16) and an air outlet (17); The mixed gas to be measured enters from the gas inlet (16) and exits from the gas outlet (17); the detection element is used to detect the acoustic wave signal generated by being absorbed by the mixed gas to be measured, the acoustic wave signal generated and detected by the laser passing through the high-concentration target gas sealed chamber (13) is the reference photoacoustic signal, and the acoustic wave signal generated and detected by the laser passing through the pure nitrogen sealed chamber (14) is the measurement photoacoustic signal.

8. The photoacoustic gas detection device based on gas filtering according to claim 7 is characterized in that: The detection element is one of a photoacoustic cell, a tuning fork quartz crystal oscillator or a cantilever beam.

9. A photoacoustic gas detection method based on gas filtering, characterized in that: Utilizing the photoacoustic gas detection device based on gas filtering as claimed in any one of claims 1 to 8 to detect the mixed gas to be detected, and obtaining a reference photoacoustic signal and a measurement photoacoustic signal; The concentration of the mixed gas to be measured is determined by using the difference between the reference photoacoustic signal and the measured photoacoustic signal.

10. The photoacoustic gas detection method based on gas filtering according to claim 9, characterized in that: The step of determining the concentration of the mixed gas to be measured by using the difference between the reference photoacoustic signal and the measured photoacoustic signal comprises: The difference between the reference photoacoustic signal and the measured photoacoustic signal is substituted into the concentration calculation formula to calculate the concentration of the mixed gas to be measured. The concentration calculation formula is expressed as: α=σN Where N is the concentration of the target gas in the mixed gas to be measured, σ is the absorption cross section of the target gas in the mixed gas to be measured, and α gas is the absorption coefficient of the target gas in the mixed gas to be measured, S mea is the measured photoacoustic signal, S ref is the reference photoacoustic signal, I0(λ) is the laser intensity, λ gas Indicates the wavelength range where only the target gas absorbs. α is the general expression of the absorption coefficient of the target gas in the mixed gas to be measured. α=α gas , λ is the wavelength variable.

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